Net primary productivity and rain‐use efficiency as affected by warming, altered precipitation, and clipping in a mixed‐grass prairie

Abstract

Grassland productivity in response to climate change and land use is a global concern. In order to explore the effects of climate change and land use on net primary productivity (NPP), NPP partitioning [fBNPP , defined as the fraction of belowground NPP (BNPP) to NPP], and rain-use efficiency (RUE) of NPP, we conducted a field experiment with warming (+3 °C), altered precipitation (double and half), and annual clipping in a mixed-grass prairie in Oklahoma, USA since July, 2009. Across the years, warming significantly increased BNPP, fBNPP , and RUEBNPP by an average of 11.6%, 2.8%, and 6.6%, respectively. This indicates that BNPP was more sensitive to warming than aboveground NPP (ANPP) since warming did not change ANPP and RUEANPP much. Double precipitation stimulated ANPP, BNPP, and NPP but suppressed RUEANPP , RUEBNPP , and RUENPP while half precipitation decreased ANPP, BNPP, and NPP but increased RUEANPP , RUEBNPP , and RUENPP . Clipping interacted with altered precipitation in impacting RUEANPP , RUEBNPP , and RUENPP , suggesting land use could confound the effects of precipitation changes on ecosystem processes. Soil moisture was found to be a main factor in regulating variation in ANPP, BNPP, and NPP while soil temperature was the dominant factor influencing fBNPP . These findings suggest that BNPP is critical point to future research. Additionally, results from single-factor manipulative experiments should be treated with caution due to the non-additive interactive effects of warming with altered precipitation and land use (clipping).

Comparison of evapotranspiration components and water-use efficiency among different land use patterns of temperate steppe in the Northern China pastoral-farming ecotone

“…6a) were larger than those determined in Duolun County to the south of our research site (Niu et al 2011). These differences may not only be due to the temporal-spacial differences of these sites but also due to differences in the determination method of surface E as their clipping method would have considerably changed the environmental conditions closely related with E (Niu et al 2008;Niu et al 2009;Xu et al 2013). Canopy removal makes the surface soil significantly drier (Table 2) especially for the higher cover land uses (GE and C), and this results in underestimation of surface E (Knapp and Smith 2001;Huxman et al 2004), although increased soil temperature (Table 2) would cause opposite effects (Luo et al 2008).…”

“…These two cases may explain how E is stimulated by change of steppe land use. Additionally, the vapor consumption process (T or ET) would closely correlate with plant photosynthesis processes (e.g., GEP and NEE) (Chen et al 2009b;Xu et al 2013). Therefore, the influence of grassland use on the ET budget should be a key factor in determining WUE for both ecosystem and canopy scales (Brümmer et al 2012).…”

“…Previous studies have intensively analyzed how vegetation types and various environmental factors influence WUE at different spatial-temporal scales (Niu et al 2008;Xu et al 2013). By focusing on WUE regulated by changing environmental factors, these studies have greatly increased our understanding of the impact of potential climatic and vegetation changes on ecosystem functions (Beer et al 2009;Keenan et al 2013).…”

“…Though various controlling factors of WUE have been widely discussed in previous studies (Fisher et al 2008;Xu et al 2013), consensus lacked the conclusions on critical factors and regulation trends (Lauenroth et al 2000;Li et al 2008). The divergences might mainly be attributed to different calculation methods and scales of research (Lauenroth et al 2000).…”

Consequences of Changing Precipitation Patterns for Ecosystem Functioning in Grasslands: A Review

“…However, several other addition studies, conducted in warm and temperate arid and semi-arid systems (e.g. Harpole et al 2007;Evans et al 2011;Talmon et al 2011;Potts et al 2012;Báez et al 2013;Xu et al 2013), investigated the effect of an increase in precipitation, although this is in contrast to future climate change scenarios, with these studies generally done by mere opportunity (e.g. using intercepted precipitation from throughfall shelters) or aiming at studying the effects of inter-annual variation in precipitation.…”